Liquid supply system



y 20, 1965 s. R. TYLER ETAL 3,

LIQUID SUPBLY SYSTEM Filed July 10, 1962 2 Sheets-Sheet l I VFNT R' STMLEy R. TYLEK WILLIAM B00715 y 20, 1955 s. R. TYLER ETAL 3,195,307

LIQUID SUPPLY SYSTEM Filed July 10, 1962 2 Sheets-Sheet 2 IMvE/vnrrs TA/way T. -TYLER. WILLIAM BOoTL A Tn kzvEvs United States Patent 3,195,367 LHQUED SUPPLY SYSTEM Stanley Ralph Tyler, Cheltenham, and William domes Beetle, Cranham, England, assignors to Dowty Fuel Systems Limited, Gloucester, England, a British company Filed luly 1t 1962, Ser. No. 208,821 Claims priority, application Great Britain, July 13, 1961, 25,4843/61 6 Claims. (Cl. till-39.23)

This invention relates to liquid supply systems for supplying liquid under pressure to spill spray nozzles or spill flow dividers. The spill spray nozzle or spill flow divider comprises a swirl chamber, a liquid supply connection into the swirl chamber which induces swirl in liquid entering the chamber, a main discharge orifice at one end of the chamber from which swirling liquid leaves the chamber and the spill connection oppositely disposed to the discharge orifice through which liquid may leave or enter the chamber. This kind of spil spray nozzle or spill flow divider will for convenience be referred to as a spill nozzle. Also for convenience the term spill nozzle will refer to a plurality of spill spray nozzles or spill flow dividers connected together with a common supply connection and a common spill connection.

The object of this invention is to provide a liquid supply system for a spill nozzle which, for a moderate range of supply pressures, will be capable of giving a large range of discharge flow rates from the nozzle.

In accordance with the present invention a liquid supply system for a spill nozzle comprises a metering means adapted for adjustment to supply any measured flow rate of liquid within a range of flow rates to the spill connection, a circulating pump connected between the spill connection and the supply connection to withdraw liquid from the spill connection and deliver it at a higher pressure to the supply connection, and a variable throttle in the supply connection having an operative interconnection with the metering means which is arranged to increase the throttling effect of the throttle with increase inthe measured flow rate of liquid delivered by the metering means whereby at higher measured flow rates to cause liquid to enter the spill nozzle both through the supply connection and the spill connection.

The metering means may include a variable restriction to control flow rate to the spill connection, the variable throttle valve being adjusted by flow increasing movement of the variable restrictor to increase throttle effect in the supply connection and vice versa.

Alternatively the metering means may be adapted to control liquid flow solely by adjustment of the varying throttle. In this method of control increase of the throttling effect of the variable throttle will cause increase in discharge flow rate from the spill nozzle and vice versa.

Two embodiments of the invention will now be described for use in the supply of fuel to the spill burner nozzles of gas turbine engines. These two embodiments are illustrated separately in FIGURES 1 and 2 of the accompanying drawings.

Referring initially to FIGURE 1 a main engine driven centrifugal pump 1 delivers fuel from an inlet 2 to an output connection 3. The output connection 3 passes to an acceleration throttle 4 whose throttling effect is adjusted by means of bellows 5 mounted within a container 6 and is arranged to be sensitive to the compressor entry and exit pressure or some desired computed function of the two. Fuel having passed through the throttle enters a pipe 7 from whence it enters a controlling throttle unit 8. With this controlling throttle, centrifugal fly-Weights 9 driven by the engine move a controlling piston valve member 11 to adjust the delivered fuel flow which leaves 3,l%,37 Patented July 2%, 1955 through pipe 12. A small pipe 13 connects pressure from the output 3 of pump 1 to a casing 1 enclosing fly-weights 9 so that this higher pressure may act on the left hand end of piston valve ll. Pressure from pipe '7 acts on the right hand end of piston valve 111 and the controlling action of piston valve 11 to throttle the flow into pipe 1?; occurs in such a way that the centrifugal force exerted by the fly-weights 9 balances the endwise force exerted on the piston valve due to the pressure difference between its ends. This pressure difference is of course that existing across the throttle valve 4.

Controlled fuel from pipe 12 is connected both to the spill connection 15 of the engine spill nozzle 16 in the combustion chambers and also to the inlet 17 of an engine driven circulating centrifugal pump 13 whose output con-. nection w is connected to the supply connection 23 of spill nozzle 16 through an adjustable throttle valve 21 and pipe 22. The throttle valve 21 is spring loaded to an open condition so as normally to exert no throttle effect, and the piston 24 Within the throttle valve Zl is arranged to be subjected to pressure exerted through pipe to act against the spring loading to cause the throttle valve 21 to exert a throttling effect on the flow from pipe 19 to pipe 22. The throttle valve does not entirely close the flow passage when the piston 24 is fully displaced but rather forms a predetermined restriction in the supply flow to the spill nozzle. The pipe 25 extends from the port in the throttle valve 8 in permanent connection with a waisted portion 25 of the piston valve ll. An auxiliary throttle port 2'7 in the valve 8 controls flow through restrictor 20 from the pipe 13 to the pipe 25. The piston valve member 11 is so arranged that the throttle 27 does not begin to open until the throttle ll acting on flow between pipes '7 and 12 is partially open. A restrictor 28 bleeds fuel from the pipe 25 so that the piston 24 may slowly move under spring action to the fully open position of the throttle valve 21 when the throttle port 27 is closed. The restrictor 24 controls fuel flow into pipe 25 to ensure slow closing movement of piston 24.

The throttle valve 4, the bellows 5 and the throttle valve 8 together form an acceleration control to determine safe acceleration fuel flow to the engine under all conditions of operation and the manner in which the control is carried out is disclosed in detail in British Patent 888,328. The fuel delivered by the pipe 12 when the acceleration control is operating is always that to give safe acceleration of the engine under the particular operating conditions eXist ing. Over the lower flow range of such acceleration fuel flow the main throttle port 10 in conjunction with the piston valve 11' forms the actual means of adjusting the fuel tlow by effectively throttling the output of pump 1. Under these conditions of operation fuel supplies through pipe 12 from the throttle valve 3 enters the inlet 17 of circulating pump 18 and is entirely pumped through pipes 19 and 22 to supply connection 23 of spill nozzle 15. Independent of the volume pumped, which must leave at the nozzle discharge, a proportion of this fuel will be circulated via the spill connection of the nozzle 16 back into the inlet 17 of the circulating pump.

The supply pump 1 is so designed that it can only supply a limited pressure which of itself would not be willcient to cause effective discharge of fuel from the spill nozzles at high output flow rates if the condition of return flow from the spill connections 23 to the inlet 15 of the circulating pump is maintained. In order to obtain higher flow rates at the limited pressure available from pump 1, provision is made to reduce the rate of circulation, thus lowering system pressure and ultimately to cause the spill nozzle to operate in the augmented flow condition in which fuel enters through both the supply and spill connections. In this condition of operation a assess":

d considerably lower pressure is necessary at the supply connection for a given discharge flow from the nozzle. In order to effect a change in operation of the spill nozzle to the augmented flow condition the throttle valve 8 is so arranged that at the changeover condition the throttle port 1% is partially open when the auxiliary throttle port 27 just begins to open. Further movement of'the piston valve member 11 will then permit pressure to enter pipe 25 which will cause piston 24 to move restricting circulation so that a variable restrictive effect is exerted on fuel flowing from the outlet 19 of the pump to the inlet 23 of the spill nozzle. It will be appreciated that this restrictive effect of throttle port is obtained due .to the influence of throttle 27 on the circulating rate and hence system pressure. The relatively slow action of piston 24 enables control at port 10 to be retained. In this way a considerable range of discharge flow rates from the.

nozzle 16 may be achieved without requiring excessive pressure from the'supply pump 1.

In order to etfect constant speed control of the engine.

using the fuel system as so far described in FIGURE '1, an all-speed governor is provided which comprises engine driven fly-Weights 29 and an adjustably loaded compression spring 31 which together control a by-pass valve 32 to by-pas-s fuel from the pipe. 12 through a pipe 33 to a low pressure zone. Since this all-speed governor'is a closed loop control it will operate to control fuel flow to the engine to maintain a desired speed independently of operation of the acceleration control. However, under some conditions a large fuel flow to the engine may be required to maintain a constant speed and such a fuel fiow may be obtainable only by operation of the throttle valve 21. Undercontrol of the all-speed governor the pressure drop of fuel passing through the throttle valve 4 operates on the piston valve 11 and the centrifugal force of flyweights 9 opposes such. pressure. The throttle 10 will adjust itself to permit acceleration fuel flow into pipe 12 but at this point the all-speed governor by-passes some of this fuel leaving only sufficient to maintain the required speed. Under these circumstances piston valve 11 serves merely as a means to determine the opening of port 27 at Reference is now made to the example shown in FIG-.

URE 2 of the accompanying drawings- There is a considerable similarity with the example shown in FIGURE 1 and where possible similar reference numerals will be used. The acceleration control is designed to operate on the same principle in that fuel flow through the throttle 4 is supplied to opposite ends of the piston valve member :11 to provide a force which opposes the force developed by the fly-weights 9, and the. position of piston valve 11 determinesfuel flow to the engine.

The difference from the previous example lies in the connection from the circulating pump 18 to the spill nozzle. In this example the output 19 of the circulating pump 18 passes to a pipe 31 leading to a throttle port 32 which is controlled by the piston valve 11 in valve unit 8. Fuel from the throttle port 32 leads into the waisted portion 26 of piston valve 11 from whence it may freely flow through port 33 into a pipe 34 which leads to the supply connection 23 of spill nozzle 16. It will be seen that throttle port 32 is arranged for closure by the piston valve 11 as increased fuel flow is required. A further difference from the previous example :lies in the fact that throttle port 10 is not provided and control of fuel discharge from the nozzle is entirely by throttle port 32.

In normal operation fuel enters the circulating pump 18 at inlet 17 together with some spill flow from the spill connection 15. At minimum flow conditions port 32 is fully open. With increased fuel demand for an acceleration, throttle 32 begins to be closed to. effect throttling til way the increased discharge flow from the spill nozzle is obtained for a moderate increase in pressure from the pump 1. 7

As in FIGUREl an all-speed governor, is provided comprising fiy-weights 29 opposed by the spring 31 and this controls a by-pass valve 32 to by-pass fuel from the pipe 7. The fuel flow through pipe 7 will, during engine operation, always represent that necessary to obtain safe engine acceleration and the all-speed governor when it controls engine speed by-passes some acceleration fuel leaving suificient to maintain engine speed at the selected value. The all-speed governor has a higher speed of response than throttle valve 4 and unit 8.

It is possible to combine in one system the throttle -10 of FIGURE 1 and the throttle 32 of FIGURE 2 for operation by piston valve member lL'the throttle 10 controlling at lower acceleration fuel flows and throttle 32 controlling at higher acceleration fuel flows.

Whilst the examples show that throttle valve 4 and the unit 8 can be adjusted directly from controlling signals it will be clear that such adjustments may be made byservomotors controlled by the signals.

When the described system is'used the pump 1 need only be capable of developing a moderate pressure to cover a large range of fueldischarge flow rates from the nozzle. This in turn'enables a light constructionzof the pump 1 to be achieved and also. enables it to operate without excessive temperature rise and without requiring excessive driving power. At the same time during engine starting, substantially high fuel pressures may be developed at the nozzle as compared with known centrifugal pump systems by permitting large spill flow from the nozzle.

We claim as our invention:

1. In combination, a spill spray nozzle; means defining a liquid circulating system for the nozzle including a circulating pump having an inlet and an outlet, a supply connection between the pump outlet and the nozzle to deliver the pump output to the nozzle, and a spill connection between the nozzle and the pump inlet :to. return any spill flow to the pump; means for feeding liquid into the system at the pump inlet by way of the spill connection; metering means for sensing and controlling therate at which the liquid is fed into the system; liquid flow con-v trol means for controlling the pump output; and means connected with the metering means to cause the flow control means to reduce thepump output at a predetermined liquid feed rate into the system, and in turn produce'an augmented flow condition to the nozzle, utilizing the supply and spilliconnections, at feed rates above said predetermined feed rate.

2. In combination, a spill spray nozzle; means defining a liquid circulating system for the nozzle including a circulating pump having an inlet and an outlet, a supply connection between the pump outlet and the nozzle to deliver the pump output to the nozzle, and a spill connection between the nozzle and the pump inlet to return any spill flow to the pump; a feed pump connected to the spill connection to feed liquid into the system at the circulating pump inlet by way of the spill connection; metering means for sensing and controlling the rate atflow condition to the nozzle, utilizing the supply and spill connections, at feed rates above said predetermined feed rate.

3. The combination according to claim 2 wherein the metering means includes a metering valve in the feed connection between the feed pump and the spill connection, and a pair of pressure connections between the metering valve and the throttle valve to adjust the throttle valve in accord with the pressure drop across the metering valve.

4. The combination according to claim 2 wherein the metering means includes a metering valve in the feed connection between the feed pump and the spill connection, a throttle valve in said feed connection intermediate the metering valve and the spill connection, and a pair of pressure connections between the metering valve and the latter throttle valve to adjust the latter throttle valve in accord with the pressure drop across the metering valve.

5. A gas turbine engine fuel system comprising a spill spray nozzle; means defining a fuel circulating system for the nozzle including a circulating pump having an inlet and an outlet, a supply connection between the pump outlet and the nozzle to deliver the pump output to the nozzle, and a spill connection between the nozzle and the pump inlet to return any spill flow to the pump; a feed pump connected to the spill connection to feed fuel into the circulating system at the circulating pump inlet by way of the spill connection; a metering valve in the connection between the feed pump and the spill connection; control means operable to adjust the metering valve in accord with an engine gas pressure; a first throttle valve in the connection between the feed pump and the spill connection, intermediate the metering valve and the spill connection; control means operable to adjust the first throttle valve in accord with the pressure drop across the metering valve; control means operable to adjust the first throttle valve in accord with the speed of the engine; a second throttle valve in the supply connection; and control means operable [at a predetermined setting of the first throttle valve to cause the second throttle valve to restrict the flow of the circulating pump output to the nozzle, and in turn produce an augmented flow condition to the nozzle, utilizing the supply and spill connections, at feed rates above that provided at said predetermined setting of the first throttle valve.

6. A gas turbine engine fuel system comprising a spill spray nozzle; means defining a fuel circulating system for the nozzle including a circulating pump having an inlet and an outlet, a supply connection between the pump outlet and the nozzle to deliver the pump output to the nozzle, and a spill connection between the nozzle and the pump inlet to return any spill flow to the pump; a feed pump connected to the spill connection to feed fuel into the circulating system at the circulating pump inlet by Way of the spill connection; a metering valve in the connection between the feed pump and the spill connection; control means operable to adjust the metering valve in accord with an engine gas pressure; a throttle valve in the supply connection; control means operable to adjust the throttle valve in accord with the pressure drop across the metering valve; and control means operable to adjust the throttle valve in accord with the speed of the engine, said latter two control means being operable to cause the throttle valve to restrict the how of the circulating pump output to the nozzle so as to produce an augmented flow condition to the nozzle, utilizing the supply and spill connections, at feed rates above a predetermined feed rate.

References Cited by the Examiner UNITED STATES PATENTS 2,737,015 3/56 Wright 39.28 2,968,151 1/61 Abraham 6039.28 3,073,046 2/63 Tyler 239--126 3,085,397 4/63 Jubb 6039.28

FOREIGN PATENTS 742,8 15 l/ 5 6 Great Britain. 843,344 8/60 Great Britain.

SAMUEL LEVINE, Primary Examiner.

ABRAM BLUM, Examiner. 

5. A GAS TURBINE ENGINE FUEL SYSTEM COMPRISING A SPILL SPRAY NOZZLE; MEANS DEFINING A FUEL CIRCULATING SYSTEM FOR THE NOZZLE INCLUDING A CIRCULATING PUMP HAVING AN INLET AND AN OUTLET, A SUPPLY CONNECTION BETWEEN THE PUMP OUTLET AND THE NOZZLE TO DELIVER THE PUMP OUTPUT TO THE NOZZLE, AND A SPILL CONNECTION BETWEEN THE NOZZLE AND THE PUMP INLET TO RETURN ANY SPILL FLOW TO THE PUMP; A FEED PUMP CONNECTED TO THE SPILL CONNECTION TO FEED FUEL INTO THE CIRCULATING SYSTEM AT THE CIRCULATING PUMP INLET BY WAY OF THE SPILL CONNECTION; A METERING VALVE IN THE CONNECTION BETWEEN THE FEED PUMP AND THE SPILL CONNECTION; CONTROL MEANS OPERABLE TO ADJUST THE METERING VALVE IN ACCORD WITH AN ENGINE GAS PRESSURE; A FIRST THROTTLE VALVE IN THE CONNECTION BETWEEN THE FEED PUMP AND THE SPILL CONNECTION, INTERMEDIATE THE METERING VALVE AND THE SPILL CONNECTION; CONTROL MEANS OPERABLE TO ADJUST THE FIRST THROTTLE VALVE IN ACCORD WITH THE PRESSURE DROP ACROSS THE METERING VALVE; CONTROL MEANS OPERABLE TO ADJUST THE FIRST THROTTLE VALVE IN ACCORD WITH THE SPEED OF THE ENGINE; A SECOND THROTTLE VALVE IN THE SUPPLY CONNECTION; AND CONTROL MEANS OPERABLE AT A PREDETERMINED SETTING OF THE FIRST THROTTLE VALVE TO CAUSE THE SECOND THROTTLE VALVE TO RESTRICT THE FLOW OF THE CIRCULATING PUMP OUTPUT TO THE NOZZLE, AND IN TURN PRODUCE AN AUGMENTED FLOW CONDITION TO THE NOZZLE, UTILIZING THE SUPPLY AND SPILL CONNECTIONS, AT FEED RATES ABOVE THAT PROVIDED AT SAID PREDETERMINED SETTING OF THE FIRST THROTTLE VALVE. 